Augers for soil survey and a process of using said augers



1-962 G. H. SOKJER-PETERSEN ETAL 3,062,045

AUGERS FOR son. SURVEY AND A PROCESS OF usmc SAID AUGERS Filed June 8,1959 2 Sheets-Sheet 1 m I q Ln J? E. .ToHAA/ssmy, AND KARL- ERIK N MAN IMVENTORS BY M/MM, l/ M ATTORNEYS Nov. 6, 1962 G. H. SOKJER-PETERSEN ETAL3,062,045

AUGERS FOR SOIL SURVEY AND A PROCESS OF USING SAID AUGERS Filed June 8.1959 2 sheets shaet 2 GU. Sim-ER PETERSEN,

.wb Kw; ERIK N Iuvsuraes ATTORNEYS United States Patent "ice 3,062,045AUGERS FOR SOIL SURVEY AND A PROCESS OF USING SAID AUGERS GunnarHannibal Siikjer-Petersen, Hagagatan 34A, Orebro, Sweden; Jan ErikJohansson, Klovervagen 13, Lund, Sweden; and Karl-Erik Nyman, Osbyholm,Sweden Filed June 8, 1959, Ser. No. 818,938 4 Claims. (Cl. 73101) Thisinvention relates to an auger for soil survey and a process of usingsaid auger.

One object of the invention is to simplify the soil surveying work byproviding a new implement which makes it possible in a single boringoperation both to obtain a reliable value of the shear strength and totake strata samples suitable for laboratory testing as well as todetermine the character of the friction or cohesion materials of thestrata through which the anger is driven.

The invention thus primarily relates to an auger for soil surveycomprising an anger rod, an anger bit mounted on said auger rod to bedriven into the soil with the aid of said rod, the auger bit includingtwo screws, 8. lower and an upper, which are coaxially and nonrotatablyconnected together but have freedom of a limited relative axialmovement, the upper screw being fixedly connected to the auger rod andthe lower screw having a relatively high and thin thread to guarantee,when screwed into the soil, the least possible disturbance thereof.

Secondly, the invention relates to a process of making a soil surveywith the use of an auger of the above-mentioned type. This processcomprises driving the auger to the desired depth with the two screwsclose together axially, withdrawing the auger without rotation,measuring the required withdrawing force on one hand while only theupper screw is raised to the limit of the relative axial movability ofthe two screws and on the other hand while after that the lower screwalso is raised, thereby detaching a soil cylinder filling out the screwthread interstices, and calculating the shear strength of the soil fromthe difference between the force values measured during the two stagesof withdrawal.

If the auger is withdrawn completely, without rotation, an excellentsample is obtained, which consists of the soil cylinder detached andraised by the lower screw. Several samples can of course be taken fromdifferent depths in that the boring is continued in the same bore holeafter each sampling.

Whether the penetrated strata have the character of friction or cohesionmaterials can be determined by listening to the sounds transmitted bythe auger rod during boring.

The invention is illustrated by way of example on the accompanyingdrawing, in which:

FIGS. 1, 2 and 3 are side elevations of an anger bit, designed inaccordance with the invention, in difierent boring stages;

FIG. 4 is a view on a smaller scale of the auger together with a machinefor driving the auger into the soil and withdrawing it therefrom.

FIGS. 1-3 show how the auger bit is composed of a lower screw 2 and anupper screw 3. The core 4 of the upper screw 3 has a bore in its lowerend portion and thus forms a guide sleeve, while the lower screw 2 has acore 5 of smaller dimension, the upper portion of which -is guided inthe sleeve 4 for instance by means of splines in the sleeve and on thecore 5, these parts also having cooperating stops (not shown) so thatthe screws permit axial movement relative to each other over but a shortdistance, e.g. 4 cm.

As will appear from the drawing, the lower screw 2 3,062,045 PatentedNov. 6, 1962 has a small core diameter in relation to its outer diameterand besides its thread 6 is very thin: it may consist for example of asheet metal strip welded to the core. The purpose of this dimensioningof course is that the lower screw shell disturb the material throughwhich it is driven as little as possible. The upper screw 3, here shownas being two-threaded, can be constructed in a similar way, i.e. withtwo sheet metal strips 7 as threads.

The upper screw 3 is secured to an auger rod 8 which in a known mannercan be prolonged by the required numb-er of 1 m. long auger extensions.

The auger driving machine shown in FIG. 4 is provided with a drivingassembly 11 comprising a motor, preferably a silent-running electricmotor, and the necessary transmissions. The assembly has a downwardlydirected output shaft with a coupling sleeve 12 for engaging the upperend of the auger rod, and the entire driv ing assembly is verticallymovable, guided on the frame of the auger machine, to load the auger byits weight. The assembly 11 is connected by a cable to a winch 13 whichpermits regulation of the load on the auger and raising the assembly towithdraw the auger. Connected between the cable and the assembly 11 is adynamometer 14 so that the vertical force on the anger is alwaysreadable. Preferably, the dynamometer is equipped with a peak indicatorso that the peak of the withdrawing force can be determined withcomplete safety, or with a device continuously recording the withdrawingforce.

In the embodiment shown the auger driving machine has a fixed nut 9 anda threaded auger extension 10 which is screwed down through the nut 9and connected to the output shaft of the driving assembly 11 in order toform, during the entire boring operation, the uppermost portion of theextended auger rod. The nut 9 and the extension 10 have the same pitchas the screw 2 and thus cause it to penetrate precisely by one pitch perrevolution, thus eliminating any tendency of the screw to tear loose anddisturb the surrounding soil. The nut 9 is of such a design as to permitopening or removing it from the frame for withdrawal of the auger rodfrom the bore hole in an unhampered manner and without rotation.

FIGS. 1-3 show different stages of such a soil survey for which theanger has been specifically developed. It is assumed in FIG. 1 that theauger is driven to a level where the shear strength is to be determined,While the screws 2 and 3 are in a moved-together position. For thispurpose the upper screw 3 may have a slightly higher pitch than thelower one 2. In FIG. 2 the auger rod with the upper screw 3 has beenwithdrawn the short distance, e.g. 4 cm., possible without raising ofthe lower screw 2 which thus remains in position in the soil. Duringthis first withdrawing stage the operator observes the withdrawing forcewhich is practically constant after the upper screw 3 has detached thesoil cylinder in which it is embedded. The withdrawal is continued andthe required force continually observed, the lower screw 2 shearingloose the soil cylinder surrounding it, and a comparison of the valuesof the withdrawing force observed gives an indication of the shearstrength of the soil around the lower part of the auger bit, all sourcesof error being practically eliminated.

Should a sample be desired for laboratory testing, the auger iswithdrawn completely without rotation, and the soil cylinder carriedalong by the lower screw 2 gives an excellent testing material. In anycase, the boring can be continued in the same bore hole, the shearstrength determined and samples taken at all desired depths.

With suitable dimensions and after calibration the described auger canalso be used for What is usually termed probing, it being possible todetermine the shear strength by measuring torques instead of withdrawingforces and thus to simplify the procedure to the detriment of theexactitude which may, however, be expected to become better than withthe use of an ordinary probe. The twoprocesses of using the auger may beemployed alternately at one and the same boring, exact determinationsbeing made at given depths and more approximate ones at other depths.Consequently, the auger may rightfully be termined a universal tool forsoil survey.

What we claim and desire to secure by Letters Patent 1. An auger forsoil survey comprising an auger rod, an auger bit mounted on said augedrod to be driven into the soil with the aid of said rod, said auger bitincluding two screws, a lower and an upper, which are coaxially andnon-rotatably connected together, said screws being movable relative toeach other axially of said auger, and means acting on at least one ofsaid screws limiting the movement of said screws away from each other,the upper screw being fixedly connected to the auger rod and the lowerscrew having a relatively high and thin thread to guarantee, whenscrewed into the soil, the least possible disturbance thereof.

2. An auger as claimed in claim 1 wherein the upper portion fthe augerrod has a thread of the same pitch as the lower screw in order to bedriven during boring through a fixed nut, thus causing said screw topenetrate the soil corresponding to its pitch.

3. A process of making soil surveys with the use of an auger comprisingan auger rod, an auger bit mounted on said auger rod to be driven intothe soil with the aid of said rod, said auger bit including two screws,a lower and an upper, which are coaxially and non-rotatably connectedtogether and are movable axially relative to each other for only alimted distance, the upper screw being fixedly connected to the augerrod and the lower screw having a relatively high and thin thread toguarantee, when screwed into the soil, the least possible disturbancethereof, said process comprising rotatably driving the auger to thedesired depth with the two screws close together axially, withdrawingsaid auger while holding it against rotation only sufiiciently far tomove the two screws apart to the limit of their relative movement,measuring the required withdrawing force while only the upper screw israised to the limit of the relative axial movability of the two screws,and then withdrawing the auger further while holding it againstrotation, thereby detaching a soil cylinder filling out the screw threadinterstices, and measuring the required drawing force, whereby the shearstrength of the soil can be calculated from the difierence between theforce values measured during the two stages of withdrawal.

4. An auger bit adapted to be attached to an auger rod to be driven intothe soil for soil survey, said auger bit comprising an upper screw and alower screw having their axes aligned and being non-rotatably attachedto each other and movable relative to each other in the direction of thealigned axes, means on at least one of said screws for limiting movementof said screws away from each other, the upper screw being adapted to befixedly secured with its upper end to the auger rod, the lower screwhaving a relatively high and thin thread to guarantee, when screwed intothe soil, the least possible disturbance thereof.

References Cited in the file of this patent UNITED STATES PATENTS137,744 West Apr. 8, 1873 147,857 Morgan Feb. 24, 1874 2,875,615 UlvinMar. 3, 1959

